PROBLEM SOLVED - IT IS A SHORTED PLATE CHOKE. ANYONE INTERESTED I CAN
PROVIDE A PHOTOGRAPH. A REPLACEMENT CHOKE IS BEING SHIPPED IMMEDIATELY
FROM RF CONCEPTS.
DICK DIDDAMS - W7QHE
dickdiddams@earthlink.net
==========================================
FROM:
Message: 4
Date: Wed, 4 Jan 2012 21:33:56 -0700
From: "Dick Diddams" <dickdiddams@earthlink.net>
Subject: [Amps] ALPHA 9500 - TUBE PROBLEM?
To: "'Amps At Contesting'" <amps@contesting.com>
Cc: Dick Diddams <dickdiddams@earthlink.net>
Message-ID: <000001cccb63$3d617620$b8246260$@net>
Content-Type: text/plain; charset="us-ascii"
ALPHA 9500 - TUBE PROBLEM?
WHILE OPERATING (THURSDAY THE 29TH) ON 20M CW (1200-WATTS OUT, WITH 1:1 SWR)
THE 9500 AMPLIFIER INSTANTLY STOPPED PRODUCING RF OUT. GRID CURRENT WENT TO
ZERO AND GAIN DECREASED TO ZERO AND "NO FAULT" occurred ON THE FLT METER. I
DIDN'T THINK ABOUT RECORDING IP OR ANY OTHER PARAMETERS AT THE TIME OF THE
PROBLEM.
HOWEVER, ON THE EVENING OF THE 29TH THE FOLLOWING TESTS WERE PERFORMED.
1) WITH AMPLIFIER BEING DRIVEN TO ABOUT 1-WATT OUT, THE Ip IS
APPROXIMATELY 230ma, THE IG IS ZERO AND GAIN OF 50.
2) INCREASING AMPLIFIER DRIVE FOR 5-WATT OUT, THE IP INCREASED TO 310MA
WITH IG OF ZERO and gain of 50.
3) WHEN SLIGHTLY INCREASING THE RF DRIVE, THE FOLLOWING TAKES PLACE:
a) INSTANTANTLY THE AMPLIFIER GAIN DECREASES FROM 50 (NORMAL IS ABOUT
35) TO 0, AND
b) THE AMPLIFIER Ip INCREASED TO (310MA) BUT Ig STAYED AT ZERO
c) AT NO TIME DID THE "FLT METER" RECORD A FAULT
4) WHILE OPERATING THE AMP IN STANDBY, THE TRANSCEIVER "PASSES-THROUGH"
(A-OK) THE 9500 INTO EITHER 1) 20M ANTENNA OR 2) DUMMY LOAD WITH 100W and
SWR OF 1.1.
AS BEST as IT CAN BE DETERMINED, THERE ARE NO OTHER AMORALITIES WITH THE
9500.
I'VE CONTACTED RF CONCEPTS VIA EMAIL (THEIR CUSTOMER SUPPORT) ON THURSDAY
THE 29TH REGARDING THIS ISSUE - ONLY ACKNOWLEDGEMENT OF THE EMAIL BY RFC WAS
PROVIDING A CASE NUMBER "OF THE ISSUE".
THE AMPLIFER AND TUBE ARE STILL IN WARRANITY SO I'M TO PERFORM
TROUBLESHOOTING ON THE AMPLIFIER, UNLESS AUTHORIZED BY THE FACTORY. I DO
HAVE A FRIEND WHO HAS OFFERED TO LOAN ME ONE OF HIS 3CX1500A7 8877 TUBES TO
DETERMINE IF THE PROBLEM IS THE TUBE OR THE HARDWARE. ANY THOUGHTS ON
TRYING A DIFFERENT TUBE AND DETERMINE IF THE AMPLIFER IS A-OK.
DICK - W7QHE
dickdiddams@earthlink.net
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